1. Field of the Invention
The present invention relates in one aspect to a display device for non-prescription reading glasses, and in another aspect, to bifocal reading glasses comprising two focal distances for use while using a computer, workspace, reading the newspaper, or other activities at intermediate or about “arms distance”, and close up for normal reading distance. The display device adheres to the lenses of the glasses, as, for example, by static cling, and has viewing holes matching the optical centers of the spectacles.
2. Prior Art
OTC reading glasses have been available for many years. Most have been single vision half-eye designs to enable the wearer to look over the top for distance use, and also different straight top bifocal designs to allow the wearer to view distant images through a plano (zero power) segment without the need for removing the glasses. The problem with current over-the-counter (OTC) reading glasses is that they are not made with customized pupillary distance (PD's) as is done in custom-made spectacles. The PD of prior art bifocal glasses, as currently manufactured, depends on the geometric or mechanical center of the frame itself, wherein the optical center of the lens is centered in the geometric center of the frame. Large frames have large distances between the optical centers of the lenses. A person with a narrow pupillary distance (PD) measurement of, for example, 56 mm., could be wearing OTC reading glasses with 66 mm. optical centers. This creates up to 2 diopters of induced prism effect that would cause eyestrain and discomfort and would be outside of ANSI standards for ophthalmic lenses.
As technology has changed, the need for an additional focal power has become a necessity. There is, therefore, a need for glasses wherein the total reading power of the spectacles is split into the two different sections of the lens. This feature is not currently available in OTC spectacles.
As the age of the population increases, many people with otherwise healthy eyes are becoming presbyopic: a loss of the eyes' ability to see objects close up such as small print and reading materials. Presbyopes currently must get an eye exam in order to acquire glasses for computer use if they want more than one power in their glasses, because this type of spectacles have not been available OTC, and need to be custom made.
A common complaint of presbyopes is that while they don't need any corrective lenses for distance use, they do need correction for near and mid-range use. Such users report that currently available OTC reading glasses are not satisfactory for either computer use or for mid-range viewing (an area of circumference less than an arms distance around wearer). Presbyopes use a lower power reading glass for the computer, and a stronger power reader for normal reading distance, because current OTC reading glasses only come in a single reading power. The computer display is generally a slightly farther distance for the user than normal reading distance, requiring just slightly less plus power correction, causing eyestrain and fatigue. The reading power is too strong and the person at a computer needs to get their eyes closer to the video display terminal than is comfortable.
Currently, computer glasses are prescribed by ophthalmologists and optometrists, usually splitting ½ of the reading power and putting it on the distance portion of the lens (for use at intermediate distance) and then cutting the power of the bifocal segment by ½, i.e., the top section of the bifocal lens is +1.50 D and the bifocal add segment is a +1.50 D for a total reading power of +3.00.
The “Continuum” progressive computer lens, manufactured by Sola International, takes the total add power needed for reading and then subtracts 1.00 diopter of power to lengthen the focal distance to accommodate use at a computer and workstation in the upper section of the lens. The Continuum lens is designed to be fitted by an optician similarly to a progressive multi-focal design.